Acry

With the rise of the dupes across many servers, and the numerous threads that keep popping up I figure it would be best to consolidate some info about it all into one post for the community's viewing pleasure, and keep the discussion contained to one thread so everyone can see what is going on.
How exploits work

Simply, exploit is just another word for bug; except, it is abused in a malicious way, or in an unintended way. They are methods that allow you to trick the server into doing something it is not supposed to. These are usually fixed by monitoring how they are done, and then adding checks against these.

Exploits can occur from the simplest things. Sometimes, the smallest bug you find can be used in another method to cause a huge exploit.

Exploits do not require server side access. This is a common misconception.

Sometimes, they just can't be fixed unless someone is observed during the process or it is leaked.

Dupe Information

Dupes are currently hitting servers in "waves". There doesn't seem to be any indication of where they are specifically coming from, but they're more than likely gold selling companies that have purchased an exploit on how to do them. There was an exploit leaked a couple weeks ago that was fixed immediately. It seems that there is more though as the waves keep happening, and in more volume than they were ever before.

Exploits for dupes can work for various items, or only certain types such as: Stackables only (Queen's Garnet) Single use items only (Mounts, etc)

Blizzard's stance at this time that has been observed

Blizzard has seem to of gone with the "If you know it's too good to be true, don't do it. You won't get anything back if we see that you knew that." when they remove them from your inventory you will be SOL with no gold returned. This means..

Buy only VIA AH. You have 100% claim to ignorance if you buy a batch off when they remove them from your inventory. They will more than likely refund any gold you spent on them if they remove them

They don't seem to be acknowledging that these dupes exist. Anyone with TUJ, and common sense can tell that they are happening.

Honestly, it is suggested that you avoid these, and report them. It is really not worth the hassle, and it is hurting the economy. If you do indulge in these dupe waves keep in mind that Blizzard can at anytime change their stance on this, and start punishing the players that buy this stuff in mass.